THE REAL ERROR OF CYRIL BURT
of environment, and the test scores may provide just another (and
more imperfect) measure of the same thing. Burt used the corre-
lation between two criteria as evidence for heredity without ever
establishing that either criterion measured his favored property.
In any case, all these arguments for heredity are indirect. Burt
also claimed, as his final proof, a direct test of inheritance: the boys'
measured intelligence correlated with that of their parents:
Wherever a process is correlated with intelligence, these children of
superior parentage resemble their parents in being themselves superior.
... Proficiency at such tests does not depend upon opportunity or train-
ing, but upon some quality innate. The resemblance in degree of intelli-
gence between the boys and their parents must, therefore, be due to
inheritance. We thus have an experimental demonstration that intelli-
gence is hereditary (1909, p. 181).
But how did Burt measure parental intelligence? The answer,
remarkable even from Burt's point of view, is that he didn't: he
merely assumed it from profession and social standing. Intellec-
tual, upper-class parents must be innately smarter than tradesmen.
But the study was designed to assess whether or not performance
on tests reflects inborn qualities or the advantages of social stand-
ing. One cannot, therefore, turn around and infer intelligence
directly from social standing.
We know that Burt's later studies of inheritance were fraudu-
lent. Yet his early and honest work is riddled with flaws so funda-
mental that they stand in scarcely better light. As in the 1909 study,
Burt continually argued for innateness by citing correlations in
intelligence between parents and offspring. And he continually
assessed parental intelligence by social standing, not by actual tests.
For example, after completing the Oxford study, Burt began a
more extensive program of testing in Liverpool. He cited high cor-
relations between parents and offspring as a major argument for
innate intelligence, but never provided parental scores. Fifty years
later, L. S. Penrose read Burt's old work, noted the absent data,
and asked Burt how he had measured parental intelligence. The
old man replied (in Hearnshaw, 1979, p. 29):
The intelligence of the parents was assessed primarily on the basis of
their actual jobs, checked by personal interviews; about a fifth were also
tested to standardize the impressionistic assessments.